Salt water pit liner



Dec. 10, 1968 w H R ET AL 3,415,022

SALT WATER PIT LINER Filed Feb.

BlLLY EARL DAVIS,

EDMUND c. SCHMIDT,

WILLIAM A. SCHAEFER,

INVENTORS.

AT TORN EYw-w.

United States Patent Office Patented Dec. 10, 1962 3,415,022 SALT WATER PIT LINER William A. Schaefer, Seabrook, and Edmund C. Schmidt, Jr., and Billy E. Davis, Houston, Tex., assignors to Esso Production Research Company Filed Feb. 1, 1967, Ser. No. 613,288 9 Claims. (Cl. 52-169) ABSTRACT OF THE DISCLOSURE A salt water pit is lined with a linear comprising a sheet of a polyolefin coated with a reinforced polyester coating. The polyester is reinforced with fiber glass.

Background of the invention To conserve fresh water supply, in certain instances, it is necessary to utilize a liner in salt water pits to prevent the seepage of accumulated salt water into the fresh water table. A primary requirement of a linear, there fore, is imperviousness to salt water. Further, the liner must be resistant to crude oils and those chemicals present in oil field brine. The liner must have the further requirement of suflicieut strength and rigidity to withstand the weight and pressure placed upon it. Thus, the requirements of a liner to be fully satisfactory are rather stringent.

Summary of the invention The present invention may be briefly described as a liner for salt water pits which comprises a sheet of polyolefin coated with a reinforced polyester resin. The invention may be further described in terms of the method used to apply the liner of the present invention to the salt water pit. The method comprises applying a sheet or sheets of a polyolefin so as to cover the floor and sides of the pit. Over the sheets of polyolefin is applied a coating of a catalyzed polyester resin. When the polyester resin becomes tacky, a reinforcing mat or cloth of fiber glass is applied, on top of which is applied a second layer of catalyzed polyester resin. The reinforced polyester coating provides an imprevious but flexible liner for salt water pits. The polyolefin sheet while an integral part of the total liner is thought to provide primarily an adequate surface for the polyester reinforced coating. The layer of reinforcing fiber material such as the mat or cloth of fiber glass add flexibility and strength to the liner of the present invention.

It is the object of the present invention, therefore, to provide a liner which is not only impervious to salt water but has the strength and rigidity to withstand substantial pressures from large volumes of water, crude oil, mud and other chemicals which are placed in salt water pits.

Brief description of the drawings The invention may be further described with reference to the drawings which illustrates an isometric and crosssectional view of a salt water pit having the liner of the present invention.

Description of the preferred embodiment Referring to the drawing, a salt water pit 1 is formed, usually by digging a shallow hole in the earth and placing the removed earth upon an apron 2, the pit 1 having a floor 3 and sides 4. In the pit are placed a sheet or sheets of a polyolefin film, preferably polyethylene although polypropylene or other polyolefins may be used, to cover the floor 3 and sides 4 and extend upon the aprons 2. The individual sheets of polyolefin film 5 are placed so that they overlap l to 12 inches preferably 3 to 6 inches to provide a surface for the polyester reinforced coating.

In the event that the floor 3 or sides 4 contain high quan tities of clay or where there are rocks or there tends t be lumps caused by the nature of the soil, such as th gumbo of the Texas Gulf Area, it may be preferred t1 spread a layer of sand before laying the sheets of poly olefin film in the pit 1. By providing a fairly fiat surface the uniformity of the liner can be maintained with a sav ings in materials and cost.

After the sheets of polyolefin film 5 are applied to cove the surfaces of the pit 1, a reinforced cotaing of a poly ester resin 6 is applied over the sheets of polyolefin. Th preferred polyester resins used in forming the liner 0 thepresent invention will contain a vinyl monomer sucl as styrene to produce substantial cross-linking. A suitabl polyester resin is formed from a mixture of styrene, malei anhydride and propylene glycol which is mixed with 1 catalyst system comprising a mixture of methyl ethy ketone (MEK) peroxide and cobalt napthenate. The rat at which the resin sets is controlled by the relativ amounts of catalyst (MEK peroxide) and accelerator (co bait napthenate) which may be used in the rate of 1:: to 5:1. The catalyst system makes up less than 1% b1 Weight of the mixture, preferably between 0.2 and 0.4% The preferred set time is between 10 and 60 minutes.

The reinforced coating of polyester resin 6 is mad up of a first coating of polyester resin 7 applied to thl sheets of polyolefin film 5 so as to have a dry thicknes of between about 50 and 200 mils. A preferred amoun of resin used would yield about to mils when dry While the preferred method of applying the resin is wit] rollers, the resin may be applied. by brush, spraying, 0 other known techniques. When the coating of polyeste resin begins to become tacky, a reinforcing fiber m'ateria 8 is then spread out on top of the coating of polyeste1 resin. The preferred reinforcing fiber material is fibe. glass in the form of a mat or cloth which may be applie in sheets or strips being overlapped 1 to 12 inches, prefer ably 2 to 6 inches. A second coating of the polyester resir 9 is then applied over the reinforcing fiber material 8 Upon allowing the polyester resin to completely set, 2 very strong yet flexible liner is provided for the salt wate. pit.

To further illustrate the present invention, a descriptior of a salt water pit liner according to the present inventior will be described.

Example A test pit was dug to a size of about 42 ft. by 42 ft The floor was approximately 25 ft. by 25 ft. The deptt of the pit was about 4 ft. from ground level; but totalec' about 6 ft. when including the dirt buildup around the edges on the apron. The total area lined was about 2,40( sq. ft.

After the pit was dug out, a load of sand was spread in, the pit so as to provide a smooth surface. A large polyethylene sheet was cut so that two pieces were required to cover the floor, sides, and extend up to the apron of the pit. The polyethylene sheet was overlapped about 6 or 8 inches. To the polyethylene sheet was ap plied a light coat of a catalyzed mixture of styrene, maleic anhydric and propylene glycol polyester resin (Coo-ks Isopolyester 939 x 801). The catalyst system used wa a mixture of MEK peroxide and cobalt naphthenate used in an amount of about 0.25 percent MEK peroxide and 0.10 percent cobalt naphthenate by weight as a catalys and accelerator respectively. The catalyst system com ponents are added to separate batches of resin (usually about equal amounts of resin) which are then mixed together. When the catalyst and accelerator were mixec with the polyester resin, the material had about a one hour pot life which was more than needed to fully apply the thickness of coating necessary. After applying the irst coating'to the polyethylene sheets, a period of time :lapsed and the coating became tacky. A fiber glass mat was laid down in widths of 50 inches. As each length )f fiber glass was laid down, an overlap of about 4 to 5 nches was allowed. -As the fiber glass was laid, it was horoughly saturated with an additional coating of the aolyester resin by :means of paint rollers on extension iandles. The liner was allowed to cure overnight and nspection Was made to patch up any missed spots or treas wherein the overlapping of the fiber glass caused my problems. The entire liner covered the floor, sides, and extended up onto the apron of the pit. To provide :ven more protection, however, the edges of the liner vere covered with saind so as to prevent any seepage tnd erosion of the soil under the edges of the liner.

The lining operation was carried out by starting on me side of the pit and proceeding down into the pit hen up and out the opposite side. Another procedure would be to start at the center of the floor of the pit ind work out one side and then the other.

The present invention has been described as a salt vater pit liner. Such a salt water pit is often used in :onjunction with a drilling operation. It may also be referred to as a mud pit. However, these pits are also lsed to hold water used in secondary recovery operations )r during workover operations. Thus the pits may be 156d to store or hold water or may be used in separation )perations where water is evaporated from the pits.

The nature and objects of the present invention havng been completely described and illustrated, what we vish to claim as new and useful and secure by Letters Patent is:

1. A liner disposed in a salt pit which comprises a sheet of polyolefin which covers the floor and sides of said pit;

a coating of a polyester resin over said sheet of polya layer of reinforcing fibers for strength and flexibility;

and

a second coating of a polyester resin over said layer of fibers.

2. A liner according to claim 1 wherein said reinforcing fiber is fiber glass.

3. A liner according to claim 2 wherein said fiber glass is in the form of a mat.

4. A liner according to claim '2 wherein said fiber glass is in the form of a cloth.

5. A liner according to claim 1 wherein said polyester resin consists essentially of a mixture of styrene, maleic anhydride and propylene glycol catalyzed by a mixture of methyl ethyl ketone peroxide and cobalt naphthenate.

6. A liner according to claim 1 wherein said sheet of polyolefin is polyethylene.

7. A liner according to claim 5 wherein said sheet of polyolefin is polyethylene.

8. A liner according to claim 7 wherein said fiber glass is in the form of a mat.

9. A liner according to claim 7 wherein said fiber glass is in the form of a cloth.

References Cited UNITED STATES PATENTS 2,695,256 11/1954 Olloqui 161-231 2,944,264 7/1960 Gagne 4-172 2,981,308 4/1961 Thompson. 3,015,191 1/1962 Lucchesi 4-172 OTHER REFERENCES Polyesters and Their Applications, by Biorksten Res. Lab., published in 1956 by lReinhold Publishing Co., N.Y., pp. 21, 22, 28 and 68.

Excavating Engineer, August 1960, pp. 26, 27 and 28.

Berry Co. Publication, two pages, received in Patent Ofiice Jan. 23, 1967.

JOHN E. MURTAGH, Primary Examiner.

US. Cl. X.R. 52-309; 61-1 

